But in the hands of a passionate advocate and skillful marketer, "An Inconvenient Truth" became one of the most talked-about films of 2006 and landed among the top three money-making documentaries of all time.

John Lesher, president of specialty unit Paramount Vantage, bought the global-warming documentary after its screening at Sundance Film Festival.

"What John did was nothing short of miraculous," says Davis Guggenheim, the film's director. "He didn't sell it as a documentary; he sold it as a thriller. He found a way to tap into people's anxiety about the issue and use it as a way to get them involved."

For instance, the tagline, "By far the most terrifying film you will ever see," made the film pop in a market crowded with summer blockbusters.

Gore does his thing
Mr. Lesher enlisted help from star and former Vice President Al Gore. Mr. Gore stumped relentlessly, appearing everywhere from "Saturday Night Live" to the Cannes film festival to Wal-Mart to promote the film.

Mr. Lesher's team created a viral campaign, including a MySpace partnership giving away free tickets. An animated video with Mr. Gore and a wise-cracking character from the TV series "Futurama" became a YouTube hit, and an MTV special also boosted the film.

Other highlights included newspaper ads that listed the record-breaking temperatures of last summer to emphasize the movie's message and an issue-based website, climatecrisis.org.

"An Inconvenient Truth," which fueled an internat-ional debate, eventually earned $48.6 million worldwide. It won the Oscar for best documentary feature.